Nowadays, as stand-alone computers have become the exception rather than the rule, since almost all information systems are interconnected to form IT networks, it may often be useful to display complex IT networks in a clearly defined manner, for instance on a video display. This desire is even becoming more urgent, since the connectivity of networks is in general on the increase due to a growing number of network components needed by current application programs.
Despite the increasing complexity of networks, an administrator of an IT network still has to keep an overview, so that he/she immediately notices communication failures between two network components and is able to intervene. Hence, the administrator requires an overview diagram in which the components and the connections between them are laid out appropriately. Not only is a clear network display important for operation, it is also important for the further development of a network. If the network components are appropriately arranged, a network planner may easily recognize whether, for instance, a switch has only few connections to other network components and therefore could be used more intensively in an upgrade of the network.
For a given network topology, there is normally a variety of reasonable ways of arranging the components since the assessment of the lucidity of a network layout normally underlies subjective perception. One way of applying objective criteria is to arrange the components in such a way that, in an ideal network layout, the number of crossings of their links is minimized, which is achieved by disentangling algorithms on graphs. Software packages providing such functionalities are, for example, offered by OREAS GmbH, Cologne, Germany under the name GoVisual® and Tom Sawyer Software, Oakland, Calif., USA under the names Tom Sawyer® Analysis, Visualization and Layout.
One type of networks liable to a prescribed topology is the storage area network (SAN) which was introduced in order to enable several servers (host devices) to share storage space, to have exclusive data access or to use data on a common storage facility. A storage area network is a high-speed, special purpose network (or sub-network) which usually includes three types of network components: host devices, fabric devices (such as bridges, switches, routers and hubs) and storage devices (such as disk arrays and tape libraries), whereby the upper side of the network is made up of host devices, the lower, opposite side is made up of storage devices and the fabric devices lie in between, when depicting the network in a standardized way.
Typically, the host devices are not interconnected and the storage devices are at most interconnected for back-up purposes, whereas the fabric devices are highly interconnected and connected with both host and storage devices. Storage area networks typically include up to 50 storage devices, and up to hundreds of host devices. Storage area networks were developed in response to three major challenges that IT managers face today: firstly, data explosion which means that applications are becoming more and more complex and therefore users need a greater amount of storage space. This also means that networks should fulfill the requirement of scalability. Secondly, the cost of storage management which means that a centralized storage management system facilitates the work of the administrators and leads, by means of increased efficiency and more effective exploitation of available resources, to a reduction of costs. Thirdly, the cost of downtime is reduced by usage of storage area networks due to redundancy in the network connectivity so that individual failing network components cannot cause a total breakdown of the SAN.
Typically, a storage area network is part of an overall network of computing resources for an enterprise and is usually clustered in close proximity to other computing resources such as mainframes, but may also extend to remote locations for backup and archival storage. Therefore, a storage device may use existing communication technology such as optical fiber technology, which offers a transmission reach of up to 10 km (or more, by means of repeaters) and copper technology providing a more limited transmission reach of 50 m. These specifications are indicated to clarify the distance between individual network components and to give an idea of the overall size of the networks. SANs support disk mirroring, backup and restoration, archival and retrieval of archived data, data migration from one storage device to another, and the sharing of data among different servers in a network.